1. Field of the Invention
The present invention relates to a diffraction display device, a viewfinder display device and a camera.
2. Description of Related Art
Japanese Laid Open Patent Publication No. 2004-191415 discloses a technology that utilizes a liquid crystal hologram constituted with a refractive index diffraction optical element as a viewfinder display element of a camera. A liquid crystal hologram is achieved in the related art by forming a refractive index diffraction grating assuming a cyclically layered structure that includes refractive-index isotropic areas and refractive-index anisotropic areas within a liquid crystal plate constituted with a polymer-dispersed liquid crystal. As illuminating light enters through a side surface of the liquid crystal plate, the light becomes diffracted at the refractive index diffraction grating and exits the liquid crystal plate toward a pentaprism. The diffracted light is then used to observe characters, graphics or the like as a viewfinder display.
However, in the non-display portions around the display portion where the refractive index diffraction grating is formed so as to display characters or graphics, the material used to constitute the refractive-index isotropic areas and the material used to form the refractive-index anisotropic areas are present together in an unhardened mixed state. For this reason, the illuminating light having entered over this area becomes scattered, which then lowers the display contrast of the characters or the graphics on display, greatly compromising the functions of the optical display device.